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Adsorption at 298 K of phenol, p-cresol, m-chlorophenol, m-aminophenol, and p-nitrophenol from aqueous solutions on activated carbons obtained from an original and a demineralized bituminous coal has been studied. The adsorption capacity of the activated carbons depended on the surface area and porosity of the carbon, the solubility of the phenolic compound, and the hydrophobicity of the substituent. The relative affinity of the phenolic compound toward the surface of the carbon was related to the electron donor-acceptor complexes formed between the basic sites on the surface of the carbon and the aromatic ring of the phenol. The adsorption capacity of the carbon depended on the solution pH. As a result, the adsorption capacity began to decrease at a pH value that depended on the difference between the external and internal surface charge density, as measured by electrophoresis and pH measurement of the slurry, respectively.

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We carried out Monte Carlo simulations of the adsorption of three speciesCH4, CF4, and SF6in model pores of various sizes. By comparing the simulated isotherms, integrated over a pore size distribution, with experimental isotherms for the adsorption of these species on a microporous carbon, estimates of the pore size distribution (PSD) of the carbon were obtainedone for each adsorptive. Because the adsorptives have different molecular sizes and strengths of interaction with the adsorbent, they probe different ranges of pore size; each adsorptive thus provided a partial PSD. By combining the partial PSDs, we were able to obtain a much more complete PSD than could be obtained with a single adsorptive. Comparison of the PSDs obtained with CF4 and SF6, which substantially overlap, shows molecular sieving. By analyzing these two PSDs, using percolation theory, we extracted an estimate of the connectivity of the pore network, an important determinant of the transport properties of the solid. Our approach is applicable to microporous solids in general.